The present invention relates to the field of digital imaging, and more particularly to processing a digital image making use of a difference digital image.
The transmitting of digital images across digital communications networks is becoming increasingly important for many applications. For example, images might be stored on a network server, and downloaded to a local computer via a communications network such as the Internet, or a local area network. Due to the fact that digital images are typically relatively large in size, the transmission of the digital images can take an extensive amount of time in many cases.
In digital imaging systems, it is sometimes desirable to modify an image in some fashion. For example, an automatic algorithm can be applied to an image to determine a preferred color balance adjustment and modify the image accordingly. Other types of image manipulation algorithms would include operations such as sharpness adjustment, noise removal, tone scale adjustment, adding text labels and cropping. Sometimes these algorithms are applied automatically, and sometimes they are interactively applied according to user preferences. As such a convenient method is have the user modify the images on the user""s computer. It is also desirable that one the images are modified to have them printed on a high quality digital printer. Such a device is not often located with the user""s computer but may be connected via a computer network.
There are a number of digital imaging application scenarios of importance where an image is downloaded from a network server to a local computer via a communications network, and the image is then modified on the local computer with one or more types of image manipulation algorithms. In many cases, it is then desirable to send the modified digital image back to the network server for storage and/or printing. As a result, it is necessary to suffer the long transmission times again. This is sometimes exacerbated by the fact that some systems are even slower at transmitting digital data to a network server than they are at downloading it from the network server.
Digital imaging applications have been devised to reduce the data transmission requirements in conjunction with image manipulation software. The user modifies the images on the user""s computer and manipulation software records the image processing parameters required to make the modifications. The remote computer, which also has a copy of the images receives the image processing parameters, which represent a small amount of data, and recreates the modified digital images at the remote site. While this method of image processing can work well, it requires that all the image manipulation algorithms and their corresponding parameters be available on both the user""s computer and the remote computer. Moreover, the version of the image manipulation software must also be the same. Consequently, this method prevents arbitrary image processing manipulation modifications of the user""s images.
It is an object of the present invention to efficiently transmit an arbitrarily modified digital image to a processing site.
This object is achieved by a method for processing a digital image in a distributed manner to produce a final modified digital image, comprising the steps of:
a) providing a source digital image at a first computer;
b) providing the source digital image at a second computer;
c) modifying the source digital image at the second computer to form a first modified digital image;
d) determining a difference digital image representing the difference between the source digital image and the first modified digital image;
e) transferring the difference digital image to the first computer; and
f) combining the difference digital image with the source digital image at the first computer to form the final modified digital image.
The present invention has an advantage that a difference digital image representing the difference between a source digital image and a modified digital image is typically more compressible than the modified digital image itself. Therefore the modified digital image can be stored with a smaller amount of digital memory. Likewise, the difference digital image can be transmitted via a communications network more quickly.
It is a further advantage of the present invention that the difference digital image representing the difference between a source digital image and a modified digital image can be used in conjunction with arbitrary image enhancement algorithms.